Spectroscopic Capture and Reactivity of a Low-Spin Cobalt(IV)-Oxo Complex Stabilized by Binding Redox-Inactive Metal Ions
Abstract
High-valent cobalt-oxo intermediates are proposed as reactive intermediates in a number of cobalt-complex-mediated oxidation reactions. Herein we report the spectroscopic capture of low-spin (S=1/2) CoIV-oxo species in the presence of redox-inactive metal ions, such as Sc3+, Ce3+, Y3+, and Zn2+, and the investigation of their reactivity in CH bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis acidic metal ions to the cobalt-oxo core increases the electrophilicity of the oxygen atom, resulting in the redox tautomerism of a highly unstable [(TAML)CoIII(O.)]2− species to a more stable [(TAML)CoIV(O)(Mn+)] core. The present report supports the proposed role of the redox-inactive metal ions in facilitating the formation of high-valent metal–oxo cores as a necessary step for oxygen evolution in chemistry and biology.
What is the metal’s role? Cobalt(IV)-oxo complexes binding redox-inactive metal ions, such as Sc3+, Ce3+, Y3+, and Zn2+, are investigated in oxygenation reactions. Theory predicts that the binding of metal ions to the cobalt-oxo core increases the electrophilicity of the oxygen atom. This result supports the role of redox-inactive metal ions in facilitating the formation of high-valent metal-oxo cores as a necessary step for oxygen evolution in chemistry and biology.
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